A thread is a single sequential flow of control within a software program. Threads provide a mechanism for splitting a computational task into two or more simultaneous operations. Multithreading is a programming and execution model that allows multiple threads to exist within the context of a single computer system, sharing the systems' resources but able to execute independently. Multithreading can allow a computational task to be executed more quickly, distributed among various computing elements, and more efficiently utilize available resources.
However, a computational task may be required to execute in a particular sequence or maintain specific relationships. When such a computation task is divided into multiple threads that execute simultaneously, the required sequence or relationships can be violated. The violation of these constraints results in an incorrect or incomplete result. Consequently, maintaining the desired sequencing and relationships during execution of a computational task in a multithreaded system can be an important challenge.